From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8AC6CD3DEA6 for ; Fri, 18 Oct 2024 18:22:18 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1EBC16B00A8; Fri, 18 Oct 2024 14:22:18 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 174936B00AA; Fri, 18 Oct 2024 14:22:18 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 03C066B00AC; Fri, 18 Oct 2024 14:22:17 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id D4EF56B00A8 for ; Fri, 18 Oct 2024 14:22:17 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 25265ACC74 for ; Fri, 18 Oct 2024 18:21:53 +0000 (UTC) X-FDA: 82687542462.16.0966E77 Received: from out-185.mta0.migadu.com (out-185.mta0.migadu.com [91.218.175.185]) by imf01.hostedemail.com (Postfix) with ESMTP id 2FF1E40012 for ; Fri, 18 Oct 2024 18:22:05 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ISWYdl7x; spf=pass (imf01.hostedemail.com: domain of martin.lau@linux.dev designates 91.218.175.185 as permitted sender) smtp.mailfrom=martin.lau@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1729275588; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=aX3NnUn3UeH6nxlGLDibU44GfunoKuAgfBARM5Nx6YQ=; b=tgL72oAyvTggzHfidvn0pPTKD98CIH/YZSxmX/+sXKbt8yAOBq/W/oSe/RPKRrbjOGSJrZ ZFKnpjAylngerQMMn+QpveAdXl9TUEeYMehNwAF3W98GI2dMb3hkby2MdcQTN0b52vb9AP FOtrGg207ULBXT3mLILZCN9UC/o3ckw= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1729275588; a=rsa-sha256; cv=none; b=Wizb/X7F0gD1AelNf7hEgQiTqq6xDepi0R0itg0gZuSii7quaeLuz70XnnxZMd9mhieZEQ XcPegDMjVnVaz8174ypGbMmjjyHD4iscxisbxrO7qnffRPaYZ/cFa3PHnaMTsSqKVpQ8RV aRdEYZ03XXrh7S+ttaiA3/zlvkkL8uI= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=ISWYdl7x; spf=pass (imf01.hostedemail.com: domain of martin.lau@linux.dev designates 91.218.175.185 as permitted sender) smtp.mailfrom=martin.lau@linux.dev; dmarc=pass (policy=none) header.from=linux.dev Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1729275733; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=aX3NnUn3UeH6nxlGLDibU44GfunoKuAgfBARM5Nx6YQ=; b=ISWYdl7xe2RCvWWdBZlzAuQHys34NaB91RlKHoJSftbAhIcBUgKd3W1Au95yy4fSCqFl56 K51phyfbeZytnF7akWTGEJj2x2Nap8e4ON+XOBd1ZPhR+9Jgtj+RkSC4ZcRnI+vedNFPgD HT+31mMysD4cFpNox6amsUooFVTqBKI= Date: Fri, 18 Oct 2024 11:22:00 -0700 MIME-Version: 1.0 Subject: Re: [PATCH bpf-next 1/2] bpf: Add open coded version of kmem_cache iterator To: Namhyung Kim Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , LKML , bpf@vger.kernel.org, Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, Arnaldo Carvalho de Melo , Kees Cook References: <20241017080604.541872-1-namhyung@kernel.org> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau Content-Language: en-US In-Reply-To: <20241017080604.541872-1-namhyung@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: qo9ofy4ocx6jzpiutikp5pm4aq1z5yik X-Rspamd-Queue-Id: 2FF1E40012 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1729275725-210351 X-HE-Meta: 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 tDz5XwcC NcMjWht+OdMsirGaHEU/HFSvNx/qd/rXWj9y7S4SEZQPDqEaWMvkurQ2lf3gosmXzzTHsa/EK47ahgJcReF1+FQJ9y/HEniiD0iCM7Ov9gsEW1EM5YG+IRTvLzbGl6vPswRwTe54zs2jeCtw5woE1pKZoLIq6Miz6MkHrd+Xom2WK4oPogOuLpK8+oLUwIu1h65epHxsuXV32ZYt1GmCJ7F4w6XIlplfl6cPa9CmzT6ii6jO2DcBTrjXL28KEJ7TXYhAoNKxguNFHi4cd02eLDYi/gkZQQbyJjec0YJEuh14Q+5E= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/17/24 1:06 AM, Namhyung Kim wrote: > Add a new open coded iterator for kmem_cache which can be called from a > BPF program like below. It doesn't take any argument and traverses all > kmem_cache entries. > > struct kmem_cache *pos; > > bpf_for_each(kmem_cache, pos) { > ... > } > > As it needs to grab slab_mutex, it should be called from sleepable BPF > programs only. > > Signed-off-by: Namhyung Kim > --- > kernel/bpf/helpers.c | 3 ++ > kernel/bpf/kmem_cache_iter.c | 87 ++++++++++++++++++++++++++++++++++++ > 2 files changed, 90 insertions(+) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 073e6f04f4d765ff..d1dfa4f335577914 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -3111,6 +3111,9 @@ BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL) > BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY) > BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE) > BTF_ID_FLAGS(func, bpf_get_kmem_cache) > +BTF_ID_FLAGS(func, bpf_iter_kmem_cache_new, KF_ITER_NEW | KF_SLEEPABLE) > +BTF_ID_FLAGS(func, bpf_iter_kmem_cache_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPABLE) > +BTF_ID_FLAGS(func, bpf_iter_kmem_cache_destroy, KF_ITER_DESTROY | KF_SLEEPABLE) > BTF_KFUNCS_END(common_btf_ids) > > static const struct btf_kfunc_id_set common_kfunc_set = { > diff --git a/kernel/bpf/kmem_cache_iter.c b/kernel/bpf/kmem_cache_iter.c > index ebc101d7da51b57c..31ddaf452b20a458 100644 > --- a/kernel/bpf/kmem_cache_iter.c > +++ b/kernel/bpf/kmem_cache_iter.c > @@ -145,6 +145,93 @@ static const struct bpf_iter_seq_info kmem_cache_iter_seq_info = { > .seq_ops = &kmem_cache_iter_seq_ops, > }; > > +/* open-coded version */ > +struct bpf_iter_kmem_cache { > + __u64 __opaque[1]; > +} __attribute__((aligned(8))); > + > +struct bpf_iter_kmem_cache_kern { > + struct kmem_cache *pos; > +} __attribute__((aligned(8))); > + > +__bpf_kfunc_start_defs(); > + > +__bpf_kfunc int bpf_iter_kmem_cache_new(struct bpf_iter_kmem_cache *it) > +{ > + struct bpf_iter_kmem_cache_kern *kit = (void *)it; > + > + BUILD_BUG_ON(sizeof(*kit) > sizeof(*it)); > + BUILD_BUG_ON(__alignof__(*kit) != __alignof__(*it)); > + > + kit->pos = NULL; > + return 0; > +} > + > +__bpf_kfunc struct kmem_cache *bpf_iter_kmem_cache_next(struct bpf_iter_kmem_cache *it) > +{ > + struct bpf_iter_kmem_cache_kern *kit = (void *)it; > + struct kmem_cache *prev = kit->pos; > + struct kmem_cache *next; > + bool destroy = false; > + > + mutex_lock(&slab_mutex); I think taking mutex_lock here should be fine since sleepable tracing prog should be limited to the error injection whitelist. Those functions should not have held the mutex afaict. > + > + if (list_empty(&slab_caches)) { > + mutex_unlock(&slab_mutex); > + return NULL; > + } > + > + if (prev == NULL) > + next = list_first_entry(&slab_caches, struct kmem_cache, list); > + else if (list_last_entry(&slab_caches, struct kmem_cache, list) == prev) > + next = NULL; At the last entry, next is NULL. > + else > + next = list_next_entry(prev, list); > + > + /* boot_caches have negative refcount, don't touch them */ > + if (next && next->refcount > 0) > + next->refcount++; > + > + /* Skip kmem_cache_destroy() for active entries */ > + if (prev && prev->refcount > 1) > + prev->refcount--; > + else if (prev && prev->refcount == 1) > + destroy = true; > + > + mutex_unlock(&slab_mutex); > + > + if (destroy) > + kmem_cache_destroy(prev); > + > + kit->pos = next; so kit->pos will be NULL also. Does it mean the bpf prog will be able to call bpf_iter_kmem_cache_next() again and re-loop from the beginning of the slab_caches list? > + return next; > +} > + > +__bpf_kfunc void bpf_iter_kmem_cache_destroy(struct bpf_iter_kmem_cache *it) > +{ > + struct bpf_iter_kmem_cache_kern *kit = (void *)it; > + struct kmem_cache *s = kit->pos; > + bool destroy = false; > + > + if (s == NULL) > + return; > + > + mutex_lock(&slab_mutex); > + > + /* Skip kmem_cache_destroy() for active entries */ > + if (s->refcount > 1) > + s->refcount--; > + else if (s->refcount == 1) > + destroy = true; > + > + mutex_unlock(&slab_mutex); > + > + if (destroy) > + kmem_cache_destroy(s); > +} > + > +__bpf_kfunc_end_defs(); > + > static void bpf_iter_kmem_cache_show_fdinfo(const struct bpf_iter_aux_info *aux, > struct seq_file *seq) > {